U.S. patent application number 11/977982 was filed with the patent office on 2008-05-29 for device for determining the end of the processing time of hardenable materials.
This patent application is currently assigned to 3M ESPE AG. Invention is credited to Gerd Brandhorst, Gunter Hertlein, Hermann Nirschl, Marc Peuker, Ingo Wagner, Erich Wanek.
Application Number | 20080124680 11/977982 |
Document ID | / |
Family ID | 7660779 |
Filed Date | 2008-05-29 |
United States Patent
Application |
20080124680 |
Kind Code |
A1 |
Brandhorst; Gerd ; et
al. |
May 29, 2008 |
Device for determining the end of the processing time of hardenable
materials
Abstract
The invention relates to a measuring device which is used to
determine the end of the processing time of hardenable materials,
especially dental moulding materials, comprising a display unit and
a sensor unit which detects a modification of at least one of the
rheological properties of the material.
Inventors: |
Brandhorst; Gerd;
(Landsberg, DE) ; Hertlein; Gunter; (Seefeld,
DE) ; Nirschl; Hermann; (Ettlingen, DE) ;
Peuker; Marc; (Schondorf, DE) ; Wagner; Ingo;
(Worthsee, DE) ; Wanek; Erich; (Kaufering,
DE) |
Correspondence
Address: |
MUETING, RAASCH & GEBHARDT, P.A.
P.O. BOX 581415
MINNEAPOLIS
MN
55458
US
|
Assignee: |
3M ESPE AG
Seefeld
DE
|
Family ID: |
7660779 |
Appl. No.: |
11/977982 |
Filed: |
October 26, 2007 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10399881 |
Sep 8, 2003 |
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PCT/EP01/11767 |
Oct 11, 2001 |
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11977982 |
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Current U.S.
Class: |
433/214 |
Current CPC
Class: |
A61C 9/0006 20130101;
A61K 6/90 20200101; A61C 19/04 20130101 |
Class at
Publication: |
433/214 |
International
Class: |
A61C 9/00 20060101
A61C009/00 |
Foreign Application Data
Date |
Code |
Application Number |
Oct 23, 2000 |
DE |
100.52.542.3 |
Claims
1-8. (canceled)
9. A method for following the progress of a setting process of
dental compounds, the method comprising: providing a device
comprising: a voltage supply, a sensor unit, and a coupling
element, wherein the sensor unit senses at least one change in at
least one property of a hardenable compound and generates an output
signal; providing a dental impression tray; connecting the dental
tray to the device by the coupling element; dispensing at least one
hardenable dental compound into the dental impression tray; and
monitoring the output signal of the sensor unit during hardening of
the hardenable dental compound.
10. The method of claim 9, further comprising: preparing an
impression, wherein the device is connected to the impression tray
before or during preparing the impression.
11. The method of claim 9 wherein the output signal is generated
when a settable threshold value is exceeded.
12. The method of claim 9, wherein the sensor unit generates an
output signal in the range from 0.1 to 60 minutes after initiation
of a hardening reaction in the hardenable compound.
13. The method of claim 9, wherein the impression is prepared at a
temperature ranging from 15 to 50.degree. C.
14. A method comprising: providing a hardenable compound; bringing
the hardenable compound into contact with a surface; providing a
sensor unit that senses at least one change in at least one
property of the hardenable compound; sensing at least one change in
at least one property of the hardenable compound; and emitting a
signal as soon as a settable threshold value of at least one
property of the hardenable compound is exceeded.
15. The method of claim 14, wherein the surface comprises a surface
of an impression tray, a surface of a dynamic mixer, a surface of
cup-shaped receptacles, or a surface of hard organic tissue.
16. The method of claim 9, wherein the sensor unit is suitable for
the determination of dielectric constant, viscosity, compressive
strength, pH, conductivity, capacitance, density, temperature
and/or impedance.
17. The method of claim 9, the coupling element having the form of
a clip, a thread, a plug-in device, a spike-shaped continuation or
a magnet, and making it possible for the device to be attached in a
defined way.
18. The method of claim 9 wherein the device comprises a
transmission unit, which transmits the output signal of the sensor
unit to a receiver.
19. The method of claim 9, the sensor unit being chosen from:
oscillator crystal, capacitor, thermometer, pH electrode, torque
transducer, thermocouple, resistance meter, wire strain gage,
ultrasonic sensors.
21. The method of claim 9, it being possible for the sensor unit to
be operated independently of the voltage supply.
22. The method of claim 9 wherein the impression tray comprises an
opening via which the sensor unit of the device can be
introduced.
23. A method for following the progress of the setting process of
dental compounds, the method comprising: providing a device
comprising: a voltage supply, a coupling element, and a sensor
unit, wherein the sensor unit senses at least one change in at
least one property of a hardenable compound and generates an output
signal, wherein the sensor unit is suitable for the determination
of at least one property selected from the group consisting of:
dielectric constant, viscosity, compressive strength, pH,
conductivity, capacitance, temperature, and/or impedance; providing
at least one hardenable dental compound; and monitoring the output
signal of the sensor unit during hardening of the hardenable dental
compound.
24. The method of claim 23 further comprising: providing a dental
impression tray; dispensing the at least one hardenable dental
compound into the dental impression tray; preparing an impression,
wherein the device is connected to the impression tray before or
during preparing the impression.
25. The method of claim 24 wherein the impression is prepared at a
temperature ranging from 15 to 50.degree. C.
26. The method of claim 23 wherein the output signal is generated
when a settable threshold value is exceeded.
27. The method of claim 23 wherein the sensor unit generates an
output signal in the range from 0.1 to 60 minutes after initiation
of a hardening reaction in the hardenable compound.
28. The method of claim 23, the coupling element having the form of
a clip, a thread, a plug-in device, a spike-shaped continuation or
a magnet, and making it possible for the device to be attached in a
defined way.
29. The method of claim 23 wherein the device further comprises a
transmission unit, which transmits the output signal of the sensor
unit to a receiver.
30. The method of claim 23, the sensor unit being chosen from:
oscillator crystal, capacitor, thermometer, pH electrode, torque
transducer, thermocouple, resistance meter, wire strain gage,
ultrasonic sensors.
31. The method of claim 23, it being possible for the sensor unit
to be operated independently of the voltage supply.
32. The method of claim 23 wherein the hardenable dental compound
is prepared by mixing a basic paste and a catalyst paste.
Description
[0001] The invention relates to the use of a sensor for determining
the end of the processing time of hardenable compounds, in
particular of dental impression compounds.
[0002] To process and use impression compounds in dentistry, the
directions for use normally specify appropriate times, how the
impression compound is to be handled and when it is to be removed
from the patient's mouth.
[0003] However, the specified times for processing and the setting
behavior of the compounds are subject to various disturbing
influences in dental practice, such as the temperature in the mouth
at the time and room temperature at the time, the mixing energy
introduced or the time spent on mixing.
[0004] It is conceivable to incorporate into the polymerizable
compounds indicators which are released during the polymerization
and indicate the progress of the reaction, for example by a change
in the color intensity. Such an attempt is described in
WO-96/00560.
[0005] A disadvantage of this is that the compounds described
contain a further component, which may have adverse effects on the
desired properties. What is more, the color changing over time does
not provide a clearly definable signal of the setting process and,
moreover, requires constant visual monitoring.
[0006] DE 29 906 343 U1 attempts to solve the problem by providing
a unit for dispensing multi-component compounds which is equipped
with a timer to indicate a time relevant for the processing.
[0007] The unit described has the disadvantage, however, that the
mixed compound is likewise subject to the external influences
mentioned and consequently no clear indication is given as to when
the setting process commences.
[0008] Devices with which changes of rheological properties can be
sensed are known from DE 19 741 674 A1 or DE 19 903 753 A1.
However, these devices are not suitable for use in dentistry for
dimensional reasons alone.
[0009] It is consequently an object of the present invention to
provide a device which indicates to the user the end of the
processing time of hardenable or hardening compounds.
[0010] This object is achieved by the use of a sensor and by
providing a suitable device, as are described in the claims.
[0011] The terms "comprise" or "include" introduce an enumeration
of features which is not exhaustive. The fact that the word "a" is
used in the claims before naming a feature does not rule out the
possibility of the named features existing more than once, in the
sense of "at least one".
[0012] The expression end of the processing time is to be
understood for the purposes of the invention as meaning the time
after the expiry of which the hardenable compound has fully
hardened substantially completely as intended, and substantially no
changes of Theological properties can be observed and/or initiated
any longer.
[0013] The expression hardenable compounds comprises all compounds
which, following a polymerization reaction, for example a
free-radical, cationic or anionic addition reaction and/or
condensation reaction, and/or cement reaction, can change from a
viscous, flowable, possibly plastically deformable state into a
permanently deformed solid state.
[0014] The expression hardenable compounds preferably comprises
sealing compounds and dental compounds, in particular dental
impression compounds, based on polyethers, A- and C-silicones,
alginates and/or polyether silicones.
[0015] In the case of impression compounds, after hardening the
compound is usually in a negative form of the surface from which an
impression has been taken.
[0016] Compounds of which the setting process can preferably be
sensed by the device according to the invention usually have the
following properties before the start of the setting process: they
are pasty, highly viscous substances which, after initiation of a
hardening reaction, solidify over a time period in the range from
0.1 to 60 minutes, preferably 1 to 8 minutes.
[0017] Before the start of the setting process, such compounds
have, for example, a viscosity of class 0 to 3 as determined by the
DIN 4823 consistency test, measured with a diameter of less than 80
mm. Materials which may be mentioned as possible examples are
silicones, polyethers, epoxy resins and polyurethanes.
[0018] The Shore hardness A of the compound, measured according to
DIN 53505 15 minutes after the end of the processing time, usually
lies in the range from 20 to 110, preferably the range from 30 and
80.
[0019] Properties, in particular Theological properties, are to be
understood as meaning all properties which, when they change, can
be recorded by means of a physical and/or chemical measuring
method. These include in particular the properties of dielectric
constant, viscosity, compressive strength, pH, conductivity,
capacitance, density and/or temperature.
[0020] The preparation of a hardenable compound comprises all forms
and types of provision of the compound either by manual, mechanical
or automated mixing of different components or dispensing of the
compound from a container and initiation of the hardening
process.
[0021] Bringing into contact is to be understood as meaning the
contact of part of the surface of the hardenable compound with the
surface of a substrate to which the compound has been applied, at
least for the duration of the setting reaction.
[0022] The term indicating unit covers all units which are suitable
for informing the user of the device of a change in state of the
compound during hardening, preferably in a visual and/or acoustic
form. This includes displays, in particular with LED indicators,
and loudspeakers.
[0023] A sensor unit for the purposes of the invention is a unit
which is suitable for sensing any change in state of the compound.
This includes pH electrodes, torque transducers, oscillator
crystals, thermocouples, resistance meters, capacitors, wire strain
gages and ultrasonic sensors. The sensor unit may in principle be
of any desired dimensions. Sensors with overall sizes of less than
5 mm are preferred.
[0024] The term surface comprises all surfaces on which the
hardenable compound can be applied as intended. To be mentioned as
examples are: impression trays, cup-shaped receptacles, hard
organic tissue, such as tooth substance and jaw, dynamic mixers,
sealing joints. Not comprised are surfaces with which the compound
comes into contact during its preparation or before initiation of
the actual hardening reaction.
[0025] The sensor is preferably located in a portable unit. The
unit which includes the sensor can preferably be operated
independently of the power supply system.
[0026] Coupling elements are intended to mean elements which allow
the device to be brought into a relationship with the hardenable
compound to follow the progress of the setting process in such a
way that a reproducible result can be obtained.
[0027] Meant in particular are elements which permit secure fixing
or fastening of the device at a defined distance from a surface or
fixed in the compound applied to the surface. Suitable coupling
elements comprise threads, clips, spike-shaped continuations,
plug-in devices, magnets.
[0028] The invention thereby has the following advantages:
[0029] The method according to the invention, using the device
according to the invention, makes it possible to follow the setting
process of the compound during hardening when used as intended "in
situ", irrespective of when and how the compound was mixed.
[0030] The invention is suitable in particular in dentistry for
determining the end of the processing time of dental impression
compounds.
[0031] Dental compounds are usually prepared by mixing a basic
paste and a catalyst paste. Depending on the mixing ratio and the
substances, the setting process occurs at different rates.
[0032] The mixing of dental compounds usually takes place in a
static or dynamic mixer, for example according to DE 90 17 323 U or
WO 98/43727. This mixer is either fitted onto a corresponding
cartridge and/or operated with an electrically operated mixing
device into which cartridges can be inserted. Suitable mixing
devices are described in DE 29 906 343 U1 or EP 0 422 413 A. The
mixers which are used are disposable mixers, since the hardened
compound cannot be removed entirely from the mixer without the
mixer being destroyed.
[0033] Unlike measuring mixers or conveying devices used in the
industrial sector, with sensors for monitoring the maintenance of
specific Theological properties of the compound to be conveyed, the
device of the present invention is distinguished by the fact that
the determination of the change in a rheological property of the
hardenable compound either takes place by a device which can be
operated independently of the mixer and of the mixing operation or
the region or portion of the device used for mixing that comes into
contact with the mixed compound is formed as a disposable
article.
[0034] If the compound obtained by mixing is a dental impression
compound, it is preferably used to fill a dental impression tray,
which is subsequently placed into the mouth cavity of a patient.
After setting, the impression tray is removed from the mouth and a
positive model is prepared from the impression taken. If the
impression tray is removed before the end of the processing time or
the end of setting, the result is unusable. If the impression tray
is left too long in the patient's mouth, removal is made much more
difficult. Knowing the best point in time for removal is
consequently important. In addition to this, the physical and
psychological strain on the patient can be reduced to the necessary
minimum.
[0035] In particular when impression compounds are used to take an
impression from hard organic tissue, it is important that, during
the setting process and during the hardening reaction, the
impression compound is not moved in the region of the surface from
which the impression is to be taken, to allow a faithfully detailed
impression to be ensured.
[0036] The invention consequently makes it possible to determine
the end of the processing time preferably under the conditions
which prevail in the patient's mouth cavity, with the consequence
that the hardened compound produces an optimum impression, since it
can be ensured that it is not removed before setting is at an
end.
[0037] The end of the processing time of the compound can be
determined for example in the following way:
[0038] To determine the progress of the setting process, the device
is expediently joined to the surface to which the hardenable
compound has been applied, for example of an impression tray, at
the point at which the hardening compound is at its coldest. This
ensures that the progress of the setting process is followed in the
region of the compound that hardens last.
[0039] The device is, furthermore, preferably chemically and/or
thermally sterilizable.
[0040] In a preferred embodiment, the device has a transmitter,
which transmits the data sensed by the sensor unit wirelessly to a
receiver unit, which is separate from the device according to the
invention. This permits further miniaturization of the device on
the one hand and external monitoring of the progress of the setting
process on the other hand. The transmission of the data can,
however, also take place in a conventional way via a connection
cable.
[0041] This allows the dentist taking an impression from a row of
teeth for example to follow the progress of the setting process via
a portable receiving device from another consulting room. Manual
monitoring by feeling the impression compound in the mouth of the
patient is no longer required.
[0042] It is also conceivable for the voltage supply, the
electronics and the sensor to be formed in such a way that they can
be integrated in a miniaturized type of construction in the region
of the surface onto which the hardenable compound has been applied,
for example into an impression tray. The data transmission to the
mixing unit can then take place for example by means of telemetry.
In the mixing unit itself is the evaluation unit, which
acoustically or optically indicates the end of the processing time
of the hardenable compound.
[0043] If appropriate, the device itself also has an indicating
unit, which informs the user of the progress of the setting process
in an optical and/or acoustic way. It may be adequate if the
indicating unit only emits a signal when a pre-settable threshold
value is reached. Continuous information is also conceivable,
however.
[0044] The device usually also has a switch or button, by which the
measuring operation is started.
[0045] An example of a tried-and-tested sensor unit is an
oscillator crystal, which generates a torsional and/or axial
oscillation which is attenuated by the viscous properties of the
hardening compound. The sensor head, for example in the form of a
feeler, is introduced into the compound through an opening on the
front side of an impression tray. The electronics and energy supply
are for example exchangeably integrated, or are able to be
integrated, into the impression tray.
[0046] It is also conceivable for the sensor unit to be immersed
with a feeler into the compound already during mixing by a mixing
unit. For example, the mixing unit or the mixer has a second flow
path alongside the first flow path by which the compound is applied
(bypass). The device according to the invention can be integrated
into this second flow path.
[0047] It is also conceivable for the device according to the
invention to have a receptacle, preferably a disposable receptacle,
which can be discarded after use, into which a small amount of the
hardenable compound is introduced after or during mixing and
before, after or during dispensing. In the receptacle there is, for
example, a rotatable piston, which can be set in rotation by means
of an electric drive and a drive shaft. The drive shaft is coupled,
for example, to a torque transducer or a rotatable shaft, which
makes it possible to determine the torque present at the rotating
piston, which is proportional to the viscosity of the hardening
compound. It is also possible to record the change in the torque
via the current consumption of the drive.
[0048] To avoid sliding of the setting material on the rotating
piston as far as possible, the surface of the rotatable piston is
preferably roughened or has friction-increasing cams.
[0049] In a preferred embodiment, the aforementioned receptacle has
a heater, which makes it possible to carry out the measuring
operation under thermal conditions which correspond to those in the
patient's mouth cavity.
[0050] Also suitable as a miniature sensor is a capacitor, the
hardenable compound being introduced between the electrodes or
capacitor plates. The electrode spacing is in this case constant.
During the hardening of the compound, the relative dielectric
constant changes and consequently so does the capacitance of the
capacitor. The capacitor may be formed for example as a plate
capacitor. Tube capacitors are also conceivable, however. Sensors
which are based on the mode of operation of an idealized plate
capacitor are known (for example system capaNCDT from
Micro-Epsilon).
[0051] Preferred exemplary embodiments are explained below on the
basis of the drawings.
[0052] FIG. 1 shows an embodiment which uses a plate capacitor as a
sensor for following the setting process.
[0053] FIGS. 2, 3 show embodiments which allow the setting process
to be followed contactlessly.
[0054] FIG. 4 shows a measuring curve, obtained by plotting the
output-signal of a capacitor sensor against the processing time of
the hardenable compound
[0055] FIG. 5 shows a possible embodiment of a portable measuring
device.
[0056] FIG. 6 shows an embodiment in which the device from FIG. 5
is integrated into a dental impression tray.
[0057] In the preferred embodiment according to FIG. 1, a sleeve
(2), for example made of brass, metal or plastic, is fitted over
the sensor (1) in order to obtain a defined measuring volume. This
is fixed by the cross section of the sensor and height of the
sleeve. The measuring chamber prepared in this way is filled with
the compound (3) up to the rim. The compound to be investigated
consequently has a defined layer thickness (=height of the sleeve).
The sleeve itself has no significant influence on the measurement,
as long as it does not lie in the region of the field lines. The
sensor unit is in connection with electronics via a connection
(4).
[0058] In the embodiment according to FIG. 2, the setting process
is followed contactlessly by means of the sensor. In this
embodiment, the capacitive sensor has no direct contact with the
hardenable compound. The compound (3) to be measured is located in
a separate measuring chamber (2), which is produced for example
from plastic. In this embodiment, the sensor (1) senses not only
the compound to be measured itself but also the capacitance of the
wall of the housing of the measuring chamber (2). Since the
capacitance of the wall of the housing does not change during
setting, the relative change in the output voltage is produced only
by the change in the relative dielectric constant of the hardening
compound. The method can consequently be regarded as
contactless.
[0059] It is also conceivable for the measuring chamber (2) to be
open and the capacitor sensor (1) to be separated from the compound
to be measured only by a layer of air (5) (FIG. 3).
[0060] In FIG. 4, the output signal (volts) of the capacitive
sensor is plotted as a function of the processing time (minutes).
At the point in time A, the compound is still viscous, at the point
in time B it has fully hardened. An initially proportionally rising
output voltage which, toward the end of the processing time of the
compound, asymptotically approaches a limit value is obtained. The
time in which the output voltage changes by a defined value in
relation to the starting value correlates with the processing time.
The variation in the output voltage as a function of the processing
time additionally makes it possible to make statements also about
the setting characteristics of the compound measured (slope of the
measuring curve).
[0061] A device for determining the end of the processing time of
hardenable compounds which are brought into contact with a surface
has, according to FIG. 5, for example a switch (1), a voltage
supply (2), evaluation electronics (3), an optical indicator (4),
activation electronics (5), a trimming potentiometer (6) and a
sensor unit (7), for example an oscillator crystal or a capacitive
sensor.
[0062] The device according to FIG. 5 is integrated into the tray
according to FIG. 6, or attached to it. The tray (8) has a usually
channel-shaped surface (9), onto which the hardenable compound is
applied. In the front region of the tray there is an opening (10),
via which the oscillator crystal (7) can be the immersed in the
compound. The device can be coupled to the tray, for example by
means of a magnet, a clip or a thread.
* * * * *